共价三嗪框架的结构调控及其光催化析氢机理研究

【作者】 吴鹏；

【导师】 李绍元； 杨玺；

【作者基本信息】 昆明理工大学 ， 材料与化工（专业学位）， 2024， 硕士

【摘要】 传统化石能源的大规模使用导致全球面临严重的能源短缺,并伴随着有害气体的排放,对人类健康和自然环境造成了不可逆转的危害。氢能作为一种高能量密度的清洁、可再生新型能源,几乎可以实现工业生产和应用的零排放,被视为应对全球能源短缺与环境污染挑战中极具潜力的能源类型之一。光催化技术是一种利用太阳能直接将水分解成氢气和氧气的技术手段。通过光催化技术,太阳能可以直接转化为化学能,实现氢气的可持续生产。这种技术具有广阔的应用前景,为解决能源与环境问题提供了新的思路和解决方案。共价三嗪框架（CTFs）因其高固氮含量、可修饰的骨架、高度可控的孔隙结构、有序的二维结构、优异的光学性能和卓越的化学稳定性而备受关注,成为光催化材料中备受关注的一种。然而,CTFs光催化剂因其光吸收范围受限、电子传输效率不高、催化活性有待提高以及材料稳定性等问题,从而限制了其进一步大规模的应用。本论文旨在通过引入官能团修饰CTFs和对CTFs的堆叠模式进行转换以增强其光催化析氢活性,重点探究官能团修饰对其能带结构和光催化析氢性能的影响以及不同堆积模式对CTFs光催化析氢性能的影响,并采用实验结合理论计算的方法,对其具体的影响机制进行研究。具体研究内容如下:（1）为了揭示官能团对CTFs材料光催化析氢性能的影响,对吸电子基团（-F）和给电子基团（-CH₃）修饰的CTFs催化剂光催化析氢性能和影响机制进行了研究。实验结果表明,引入官能团修饰可以有效增强CTFs光催化剂对可见光的响应范围、降低带隙,并进一步增强其光电转换效率及光生载流子的分离和迁移能力。通过实验发现,吸电子基团（-F）修饰的CTF-F表现出更佳的析氢还原电位和光电转换效率,以及光生载流子的分离和迁移能力。这种优异的光电性质使得CTF-F具有最佳的光催化析氢性能,其光催化析氢速率达5089.79μmol g^-1 h^-1,并且在循环稳定性测试中表现出良好的稳定性。（2）为了进一步探究了堆叠模式的差异对于CTFs光催化析氢性能的影响机制。采用不同的制备方法,在几乎相同的反应条件下,成功实现了一步制备具有AB堆积结构和AA堆积结构的CTF-AB和CTF-AA。通过一系列基本表征手段验证了这两种堆叠模式CTFs光催化剂的成功制备,并对它们的光催化析氢性能和循环稳定性进行了研究。研究发现,相较于CTF-AB,CTF-AA具有更强的光响应能力、更窄的带隙结构和更优越的析氢还原电位。实验结合DFT理论计算揭示了CTF-AA具有更优异的光电转换效率和光生载流子的分离和迁移能力,阐明了堆叠模式对于CTFs光催化性能的影响机制。在可见光条件下,CTF-AA表现出更优异的光催化活性,析氢速率达到4691.73μmol g^-1 h^-1,约为CTF-AB的1.4倍。此外,经过32小时8个循环测试后,CTF-AA的光催化活性未见明显下降,而CTF-AB的光催化活性下降十分明显,验证了其具有更优异的结构稳定性。更多还原

【Abstract】 The widespread use of traditional fossil fuels has led to a severe global energy crisis and accompanied emissions of harmful gases,causing irreversible harm to human health and the natural environment.Hydrogen energy,as a clean and renewable energy source with high energy density,can achieve nearly zero emissions in industrial production and application,making it one of the most promising solutions to global energy crises and environmental pollution.Photocatalysis is a technique that utilizes solar energy to directly decompose water into hydrogen and oxygen.Through photocatalysis,solar energy can be converted directly into chemical energy,enabling sustainable hydrogen production.This technology holds broad prospects for application,providing new insights and solutions for addressing energy and environmental issues.Covalent triazine frameworks（CTFs）have attracted attention as photocatalytic materials due to their high nitrogen content,modifiable framework,highly controllable porous structure,ordered two-dimensional structure,excellent optical properties,and outstanding chemical stability.However,issues such as limited light absorption range,low electron transfer efficiency,the need for improvement in catalytic activity,and material stability constrain further large-scale applications of CTFs photocatalysts.This thesis aims to enhance the photocatalytic hydrogen evolution activity of CTFs by introducing functional group modifications and transforming the stacking modes of CTFs,focusing on investigating the effects of functional group modifications on their band structure and photocatalytic hydrogen evolution performance,as well as the influence of different stacking modes on the photocatalytic hydrogen evolution performance of CTFs.Experimental methods combined with theoretical calculations are employed to study the specific mechanisms of these influences.The specific research contents are as follows:（1）To elucidate the effects of functional groups on the photocatalytic hydrogen evolution performance of CTFs,the photocatalytic hydrogen evolution performance and influencing mechanisms of CTFs catalysts modified with electron-withdrawing groups（-F）and electron-donating groups（-CH₃）were studied.Experimental results demonstrate that the introduction of functional group modifications can effectively enhance the light response range of CTFs photocatalysts,reduce the bandgap,and further enhance their photoelectric conversion efficiency and the separation and migration ability of photogenerated charge carriers.It was found experimentally that CTF-F,modified with the electron-withdrawing group（-F）,exhibits superior hydrogen evolution reduction potential,photoelectric conversion efficiency,and separation and migration ability of photogenerated charge carriers.These excellent photoelectric properties make CTF-F exhibit the best photocatalytic hydrogen evolution performance,with a hydrogen evolution rate of 5089.79μmol g^-1 h^-1,and it shows good stability in cycling stability tests.（2）To further explore the effect mechanism of different stacking modes on the photocatalytic water splitting hydrogen evolution performance of CTFs.Using different preparation methods,under almost the same reaction conditions,successful preparation of CTF-AB with AB stacking structure and CTF-AA with AA stacking structure was achieved.Through a series of basic characterization techniques,the successful preparation of these two stacking mode CTFs photocatalysts was verified,and their photocatalytic hydrogen evolution performance and cycling stability were studied.The research found that compared to CTF-AB,CTF-AA has stronger light response capability,a narrower bandgap structure,and a superior hydrogen evolution reduction potential.Experimental combined with DFT theoretical calculations revealed that CTF-AA has superior photoelectric conversion efficiency and the separation and migration ability of photogenerated charge carriers,elucidating the influence mechanism of stacking modes on the photocatalytic performance of CTFs.Under visible light conditions,CTF-AA exhibits superior photocatalytic activity,with a hydrogen evolution rate reaching 4691.73μmol g^-1 h^-1,approximately 1.4 times that of CTF-AB.Furthermore,after 32 hours of 8-cycle tests,the photocatalytic activity of CTF-AA showed no significant decrease,while the photocatalytic activity of CTF-AB decreased significantly,verifying its superior structural stability.更多还原